Friday, July 29, 2016

White Dwarf Lashes Red Dwarf Every Two Minutes

From Ideas, Inventions and Innovations:

Astronomers using the NASA/ESA Hubble Space Telescope, along with other
telescopes on the ground and in space, have discovered a new type of
exotic binary star: in the system AR Scorpii a rapidly spinning white
dwarf star is powering electrons up to almost the speed of light. These
high energy particles release blasts of radiation that lash the
companion red dwarf star, and cause the entire system to pulse
dramatically every 1.97 minutes with radiation ranging from the
ultraviolet to radio.

In May 2015, a group of amateur astronomers from Germany, Belgium and
the UK came across a star system that was exhibiting behaviour unlike
anything they had ever encountered before. Follow-up observations led by
the University of Warwick and using a multitude of telescopes on the
ground and in space, including the NASA/ESA Hubble Space Telescope [1],
have now revealed the true nature of this previously misidentified
system.

This artist's impression shows the strange object AR Scorpii. In this
unique double star a rapidly spinning white dwarf star (right) powers
electrons up to almost the speed of light. These high energy particles
release blasts of radiation that lash the companion red dwarf star
(left) and cause the entire system to pulse dramatically every 1.97
minutes with radiation ranging from the ultraviolet to radio.

Credit: M. Garlick/University of Warwick, ESA/Hubble

The star system AR Scorpii, or AR Sco for short, lies in the
constellation of Scorpius, 380 light-years from Earth. It comprises a
rapidly spinning white dwarf [2], the same size as Earth but containing
200 000 times more mass, and a cool red dwarf companion one third the
mass of the Sun [3]. They are orbiting one another every 3.6 hours in a
cosmic dance as regular as clockwork.

In a unique twist, this binary star system is exhibiting some brutal
behaviour. Highly magnetic and spinning rapidly, AR Sco's white dwarf
accelerates electrons up to almost the speed of light. As these high
energy particles whip through space, they release radiation in a
lighthouse-like beam which lashes across the face of the cool red dwarf
star, causing the entire system to brighten and fade dramatically every
1.97 minutes. These powerful pulses include radiation at radio
frequencies, which has never been detected before from a white dwarf
system.

Lead researcher Tom Marsh of the University of Warwick's Astrophysics
Group commented: "AR Scorpii was discovered over 40 years ago, but its
true nature was not suspected until we started observing it in June
2015. We realised we were seeing something extraordinary the more we
progressed with our observations."...MORE